(1) Field of the Invention
A space frame is lightweight rigid structure constructed from struts in a geometric pattern. The struts in a space frame are connected together by hubs to form interlocking triangles. Some of the first space frames were developed by Alexander Graham Bell in 1900. The first space frame used as a geodesic dome was developed in July 1926 by Walther Bauersfield for the Carl Zeiss Optical Company in Jena, Germany, with the geodesic dome design popularized at a later date by Buckminister Fuller. A space frame is extremely strong for its weight, and is designed to be inherently stable. When a space frame is used as a geodesic dome, its shape approaches a sphere, which allows it to enclose the greatest volume for the least surface area.
The invention described in this patent is of a locking collar that supports the hubs of a space frame, with a geodesic dome being an example of one use for the invention. The large number of hubs in a geodesic dome, and the angles that the struts radiating from these hubs must have relative to the other struts and to the curvature of the dome, is the basis for describing the usefulness of this invention.
The hubs for a geodesic dome must connect the struts together at the proper angles relative to the other struts attached to the hub. Each hub facilitates a 4-way, 5-way, or 6-way connector for the struts in a geodesic dome. The total angle surrounding each hub is 360 degrees, with the number of struts radiating from the hub describing a segment of this angle. Thus, the 5-way hubs must hold the struts at an evenly spaced 72 degree angle relative to the adjoining struts, and the 6-way hubs must hold the struts at an evenly spaced 60 degree angle relative to the adjoining struts. The 4-way hubs are used at the equator of a geodesic dome to provide a rest on the ground as a foundation, and use a 60 degree angle for the struts above the foundation. This invention of a locking collar supports the correct angle of the struts that they must have relative to the other struts.
Geodesic domes come in various frequencies, with the frequencies referenced as 1V, 2V, 3V, etc. The frequency of a dome relates to the number of smaller triangles into which it is subdivided. A high frequency dome has more triangular components, more struts, more hubs, and is more smoothly curved and sphere-like than a low frequency dome.
The frequency of the dome determines the dome curvature angle that the struts will have relative to the radial plane of the hub equator. This angle determines the curvature of the dome structure. A low frequency dome with few struts will have a larger angle of inclination to the radial plane of the hub equator, while a high frequency dome with many struts will have a smaller angle, as this chart demonstrates:
Strut Angle from Radial FrequencyHubsStruts Plane of Hub Equator1 V Dome112532 degrees2 V Dome266516 to 18 degrees, depending on strut length3 V ⅜ Dome4612010 to 12 degrees, depending on strut length3 V ⅝ Dome6116510 to 12 degrees, depending on strut length4 V Dome912507 to 9 degrees, depending on strut length
Enforcing the correct strut angle relative to the radial plane of the hub equator is crucial to maintaining the spherical shape of the geodesic dome. If the hubs are not strong enough to provide the correct dome curvature angles to the struts, the dome will collapse. This invention of a locking collar provides support for each hub and keeps the struts in the correct dome curvature angles they have relative to the radial plane of the hub equator.
The struts for many domes are made from metal or PVC pipes. In the USA, these materials usually come in 3 meter lengths, which is too long for stable dome construction, and so are cut in half to 1.5 meter lengths. A 2V frequency dome with 1.5 meter struts will create a dome with a 2.4 meter radius, which is good for a small tent-like structure, and it only requires 26 hubs. To create a house-sized dome with a radius of 5.8 meters using 1.5 meter struts will require a 4V frequency design, which requires 91 hubs.
What is apparent from this information is the large number of hubs needed to create a dome for housing people or large machinery. For a 4V dome with 91 hubs, if each hub is produced for only $100.00, the cost of hubs alone would be $9,100. The high cost of the hubs defeats the purpose of constructing an inexpensive geodesic dome shelter.
This invention of a locking collar eliminates the need for the geodesic dome hubs to be built of sturdy and expensive materials to handle the angular stress applied against them.
A geodesic dome is a space frame, but space frames can designed in other shapes. One example is a space frame constructed as a “hoop house” for greenhouses, or for barns and other large buildings. This type of space frame design is a geodesic cylinder in shape, with the cylinder divided in half along its axis and laying on its side. Many well-supported hubs are needed for this design, and this invention of a locking collar relieves the stress on the hubs of a space frame in this shape as well.
This invention of a locking collar consists of the addition a simple, inexpensive support to surround each hub of a space frame. This invention relieves the stress on the hubs, which allows much simpler and cheaper hubs to be used.
(2) Description of the Related Art
In prior art, there are many types of hub designs, but they do not include a separate locking collar support system as described in this patent. This invention of a locking collar is not a hub, but a separate support system, and can work in addition to each of various hub designs that have received a United States Patent or are otherwise in use. This invention makes many of these hubs obsolete, as it allows for a simpler and much less expensive type of hub to be used for space frame construction.